1A.2 Anthony, Petrels of Southern California. F April 



well grown young the middle of May. The range of^variation 

 in breeding in these three species of Oceanodroma presents an in- 

 teresting study. The Guadaloupe Petrel, with a breeding season 

 early in March, leaves the colony altogether by June lo, by which 

 time O. socorroensis has not begun to lay, and O. melania is still 

 later. I have found the last species incubating as late as Septem- 

 ber 8. I am quite sure that only one young is raised each year, 

 though each species seems to have a rather long nesting season. 



Little attempt is made at nest building by either the Socorro 

 or Black Petrel, though a few sticks are often dtagged into the 

 burrow with an evident desire to construct something resembling 

 a nest. The Guadaloupe Petrel, however, nearly always has a 

 few dry oak leaves or pine needles at the end of the burrows I 

 have opened, it making a much better attempt at nest building, 

 owing perhaps to the fact that the burrows are dug among the 

 trees where this class of nesting material is abundant, whereas the 

 other species nest on barren islands and cannot so readily obtain 

 desirable material. 



In early June I have found the Least Petrel migrating along the 

 coast of Lower California in company with the Socorro and Black 

 Petrels, and in late July have found them nesting on the small 

 rocky San Benito Island, fifty miles off the coast of the peninsula. 

 So far I have never found the Least Petrel nesting in burrows. 

 They have always been taken from the crevices in rocky ledges 

 or among the loose stones. The pearly white egg is laid on the 

 bare rock. Usually several are found within a few feet if desira- 

 ble crevices are numerous. Young were taken as late as Septem- 

 ber 7 or 8 that were but a few days old. They were like the young 

 of the three species of Oceanodroma I have mentioned, except for 

 size. All are covered with sooty or slaty black down, through 

 Avhich the feathers appear when the bird is nearly or quite fully 

 grown. 



For the past ten years I have at times seen a small white- 

 rumped Petrel at sea as far north as southern California but more 

 common perhaps about Guadaloupe and Cerros Islands. They 

 were quite common in April and May about Socorro Island and 

 a few were seen ofif Clarion but, like veritable will-o'-the-wisps, 

 they were always just out of reach and all attempts to identify 



